Effective structural health monitoring (“SHM”) systems require large numbers of miniature, lightweight sensors capable of measuring a range of parameters. Fiber optic sensors are a promising technology to provide this measurement capability with large numbers of sensors multiplexed onto a single fiber capable of measuring of strain, temperature and ultrasonics. Fiber optic sensors provide a minimally invasive sensing capability with a greatly reduced number of interconnects and cabling, which is expected to lead to greatly improved system reliability. For example, multiplexed arrays of fiber Bragg grating sensors are capable of measuring slowly varying strain with a performance that matches existing conventional piezoelectric strain gauges (<1 microstrain).
There is also interest in measuring high frequency signals generated either by structural fatigue through crack formation, in the form of acoustic emission (“AE”), as well as actively generated signals such as Lamb waves generated by piezoelectric sources for damage detection. Piezoelectric sensor performance can be tailored in terms of their size, response and electronic amplification circuitry to provide the required performance for a given application; however, these sensors are large and are not practical to be implemented in large numbers.